While some referees are paid for their work, their careers - like those of athletes - are short, competitive, and fraught with uncertainty. Career transitions are numerous and inevitable, yet they are neither socially nor scientifically addressed. In this context, a SwafS project aimed at supporting referees' career transitions represents a major challenge for both sports organizations and research. At the crossroads of Sport Science and Education and Training Sciences, AcT-Pro Arbitres aims to co-construct tools and methods for supporting professional transitions based on a boundary object: the skills framework of high-level referees. Rooted in an enactive paradigm and activity theories, this project focuses on the ways in which the use of the skills framework enables referees to describe and support their lived experiences more explicitly and in greater detail. Thus, AcT-Pro Arbitres examines how referees are transformed by the support they receive and how the skills framework is reconfigured as they use it. In doing so, AcT-Pro Arbitres produces intermediate objects: a materialization of the evolution of the skills framework in a digital artifact and a description of the follow-up practices. These intermediate objects are collectively reworked in workshops that bring together referees, sports federation managers, vocational transition experts and researchers to co-construct a boundary object that allows each social group to invest it in relation to their own issues. The results of this project will provide the tools and the network of actors needed to achieve institutional recognition of referees' skills and profession at national level. The "sequel" project will also be part of a European context, with the submission of an Erasmus+ Sport project on the "dual careers" of referees, in order to disseminate and put into perspective the AcT-Pro Arbitres project. Beyond what remains specific to sports careers, the approach could find an echo in other professional contexts, especially in emerging professions and/or those facing short careers. AcT-Pro Arbitres provides an opportunity to test the value of starting from singular lived experiences in a professional transition process, and the added value of a dynamic formalization of professional skills discussed and legitimized by a collective of heterogeneous actors.